Rev 6/7/ BC Atomic Model Development
Democritus – 400 BC Defined an Atom as the smallest unit of a material that can not be split up Greek word “atom” means invisible Atoms are solid, homogeneous, indestructible and indivisible
Dalton’s Atom Atom = Solid sphere All elements are composed of tiny invisible particles called atoms Atoms of same element- alike & different from atoms of other elements Atoms join together in whole number ratios to form compounds.. that means they join in a definate proportion every time the same compound is formed.
Henri Becquerel 1896 © Discovered radioactivity © Radiation produced spontaneously by unstable atomic nucleus
Thomson’s Atom Discovered electrons Plum Pudding model (for us Americans it looks like a chocolate chip cookie model) Electrons - charge + charge “pudding”
Rutherford’s Atom discovered dense positively charged nucleus using gold foil experiment electrons protons Gold Foil Animation
James Chadwick 1932 Identified neutron Same mass as proton No charge
electrons orbit in energy levels around the protons in the nucleus. p+p+ Bohr’s atom like our solar system… (electrons the planets, the nucleus the sun!)
Atomic Time Line review… BC Atom -Modern Atom -Radioactivity-Electron -Positive Nucleus -Energy Levels-Neutron